In the electronics field it has become conventional to connect simultaneously plural electrical signals from one device, terminal, computer, etc., to another using multiconductor cable assemblies. Such a cable assembly typically includes a multiconductor cable and one or more cable terminations which provide electrical connections between the conductors and respective external members, such as pins, contacts, conductive paths on a printed circuit board, etc. A cable termination may be located at the end of the cable or at a location between the ends of a cable, and in the latter case sometimes the label daisy chain termination is used. The cable termination usually includes a plurality of electrical contacts, sometimes referred to as contacts, terminals, or the like, which are retained in a mechanical structure, such as a housing or some other relatively rigid body so that the contacts can be plugged into or otherwise mated with one or more appropriate external members to which electrical connection is intended. The housing usually is electrically non-conductive; or for shielding or like purpose it may be conductive, at least in part, without shorting to the signal contacts, conductors, etc.
A cable termination assembly is the combination of the cable termination and the cable itself, and typically there is provided in a cable termination assembly or in association therewith a strain relief mechanism (sometimes simply referred to as a strain relief). The object of the strain relief is to provide means for mechanically connecting the cable termination and the cable so that forces tending to separate the cable termination and the cable will tend not to be transmitted to the actual connections between cable conductors and contacts to which they are attached in the cable termination.
A cable termination located at an end of a cable typically is referred to as an end termination; one located between ends typically is referred to as a daisy chain type termination or with the cable, then, as a daisy chain assembly.
In U.S. Pat. No. 4,030,799 is disclosed a multiconductor cable termination assembly in which the plural electrical conductors (sometimes referred to as wires) of a multiconductor ribbon cable are mass terminated in a cable termination. The conductors are held in parallel with each other by insulation, the cable as a whole being in the form of what is commonly referred to as flat ribbon cable. The termination includes a plurality of electrical contacts that are mechanically and electrically connected to the cable and especially to the conductors thereof by insulation displacement connections (IDC), wherein a portion of each contact pierces through the cable insulation to engage a respective conductor. The termination also includes a strain relief body that is molded to at least part of each of the contacts and cable and which may be bonded chemically with the cable insulation for added integrity. While such cable termination assembly and cable thereof are useful for transmitting relatively low speed electrical signal, they are not as useful for transmitting relatively high speed signals due to cross talk and varying impedance conditions. Woven cable, Teflon insulation cable and like cables that provide shielding, grounding, controlled impedance, etc., are better suited for high speed signal transmission, such as high speed data transmission or the like, as is known.
A cable termination assembly that is especially suited for transmitting high speed signals is disclosed in U.S. Pat. No. 4,722,692. In such patent there is disclosed a multiconductor ribbon cable that uses a plurality of conductors to carry signals (hereinafter referred to as signal conductors for convenience) and a plurality of electrical conductors that are connected to a source of reference potential, such as ground (hereinafter referred to as ground conductors for convenience), to provide a measure of isolation between respective signal conductors and to help control impedance characteristics of the cable. Moreover, in at least one embodiment the cable insulation is made of a material, such as polytetrafluoroethylene (also sold under the trademark Teflon.RTM.), which has particularly advantageous electrical insulation, impedance, and other characteristics. A disadvantage to using Teflon is the problem encountered in connecting a cable termination or a strain relief thereto, as Teflon ordinarily does not bond to other materials.
In U.S. Pat. No. 4,722,692 the conductors of such cable are exposed by removing a portion of insulation at the end of the cable, severing and sliding another portion of the insulation along the conductors to take the place of the removed insulation portion on the conductors while exposing portions of all the conductors off which the latter insulation portion was slid, and bending (knuckling) the exposed conductor portions to form U-shape loops exposed out of the plane of the cable for connection to respective contacts. Additional slots are formed in the cable insulation, and a strain relief (e.g., of plastic material) is molded to the cable with portions of such strain relief being secured to the cable by portions of the welding material flowing through the slots to form legs in the slots. A disadvantage to such cable termination assembly and to the method of terminating such cables is the substantial amount of labor required to prepare the cable and to attach it to respective contacts of the termination. Another disadvantage is the lack of stiffness (weakness) of the conductors where they all are exposed. Other disadvantages are that all ground conductors exit the end of the cable requiring special terminating thereof and that all signal conductors are knuckled respectively above or below the plane of the cable, thus limiting the termination therefor to an in-line type that extends parallel to the cable plane.
U.S. Pat. No. 4,143,236 to Ross discloses a woven cable. The woven cable is formed of a plurality of electrical conductors (wires) each of which is independently insulated. The insulated conductors are woven in a manner similar to the way the threads of a fabric are woven, forming a multiconductor ribbon cable. The conductors are woven such that each undulates in a somewhat sinusoidal fashion with a frequency (or wavelength also known as pick length) between peaks along the axial length of the cable, e.g. along the center plane of the cable. The frequency may be selected to be longer or shorter as a function of the weaving process, and the peaks of respective conductors may be in phase, out of phase by some amount, e.g., 90.degree., 180.degree., or some other amount, or may vary in some other way, all as a function of the programmed weaving process. Threads are woven in the cable in warp (parallel with the conductors) and weft (transverse to the conductors) directions.
The conductors of such woven cable may be arranged and/or designated in a variety of relationships, e.g., the carrying of electrical signals and the providing of ground reference potential condition. In one example there may be only one ground conductor between each pair of otherwise adjacent signal carrying conductors. In another example there may be a separate dedicated pair of ground conductors for each signal conductor within the plane of the cable. This configuration then would include at the edge of the cable a ground conductor, followed by a signal conductor (as one moves inward from the edge of the cable in the plane of the cable), followed by two ground conductors, another signal conductor, two ground conductors, etc., as is known, for example, from U.S. Pat. Nos. 4,143,236 and 3,634,782 (Marshall). This type of configuration is particularly suitable for high speed signal transmission with good impedance control characteristics.
One disadvantage to the use of woven multiconductor cables is the difficulty in connecting the conductors thereof to the contacts of a cable termination. In the past each conductor was stripped of insulation at the end of the cable, and the bare conductor wire (also referred to as "cable conductor" herein without the designation "wire") was soldered to a contact or to solder pads on a printed circuit board to which contacts also were connected. That procedure was time-consuming, difficult, and expensive. Moreover, there was no convenient form of strain relief available for securing the cable to the termination in a manner that avoids applying stress or strain to the junctions of the contacts and conductors. As is known, it is difficult, if not impossible, to mold accurately to a woven material. The ability to shut off the mold so that there is no leakage, wicking, etc., is difficult if not impossible; therefore, the accuracy, completeness, etc. of a part molded to a woven material would be somewhat uncontrolled.
One type of electrical cable that is especially suited for high speed signal transmission is known as coaxial cable in which there typically is a signal carrying conductor and a surrounding conductive material that is maintained at a predetermined reference potential, such as ground. Usually the circumscribing conductive material is relatively fragile, such as a foil material, and a drain wire is positioned in engagement with such material to maintain the electrical continuity thereof in the event of a tear in such material. Another similar type of high speed signal transmission cable is referred to as a triax cable. Typical prior techniques for terminating such coaxial cables and triaxial cables required a separate cable termination for each cable, each such termination including a pair of contacts (one for the signal conductor and one for the ground), a housing for retaining the contacts, and a strain relief mechanism.
The disclosures of all of the patents mentioned herein are hereby incorporated in their entirety by reference.